Diamond is a vital natural carbon material and one of the three more common natural carbon allotropes in addition to amorphous carbon and graphite. Diamond has many excellent properties including, for example, mechanical hardness, low wear rates, chemical inertness, and thermal conductivity. Diamond also can be made synthetically by man. One way to make synthetic diamond is by chemical vapor deposition (CVD). In this process, gases containing carbon are converted to diamond and take the form of either particulates or a films (coatings), typically on a solid surface. The resulting diamond films are further typically classified by their crystalline structure. The first and dominate structural classification results from the film being either single-crystalline or polycrystalline. Polycrystalline diamond films are typically further classified by the resulting grain size, orientation, and grain boundaries features. Examples of the common classification of polycrystalline-films include microcrystalline diamond, nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD). In addition, the diamond may comprise some non-diamond carbon portions, and the percentage of the non-diamond portion can be varied. Still further, non-carbon atoms can be introduced to vary the properties. The specifics of the form, structure, and resulting properties of diamond can be dependent on the processing path and conditions. Hence, diamond is actually a family of materials, and these differences in the diamond structure can have important bearing on the application of diamond. See for example U.S. Pat. No. 5,989,511 (Argonne National Laboratory).
In some applications, the surface properties of diamond are important. For example, friction, wear, and other tribological properties can depend highly on surface metrology. In many cases, diamond having controlled surface is needed, but one may not have taken the time to evaluate precisely how the surface impacts properties. Diamond can be synthesized to have a smooth surface as made. Alternatively, diamond surface can be made more smooth by polishing. However, diamond is nature's hardest material, and polishing processes that make a diamond surface smooth can be economically costly and inefficient. Hence, a need exists to develop better, more controlled diamond surfaces and processes for making same. In particular, better tribological properties and lower sliding friction are needed. In many cases, a need exists to understand more fully the detailed relationship between diamond surface metrology and the application.
In addition, in many cases, large-scale methods of making diamond are needed which also control the surface properties. Processes useful in research may not be applicable for industrial applications. Cost efficient processes are needed.
In other applications, a need exists to deposit solid layers onto diamond.
U.S. Pat. No. 5,702,586 describes one process for polishing diamond.